package reese.think_in_java.java_21_thread;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * ***********************************************************
 *
 * @类名 : reese.think_in_java.java_21_thread.类名
 * @DESCRIPTION : 这家伙太懒啥都没写
 * @AUTHOR :  一个风情万种的男子
 * @DATE : 2016/6/1
 * ***********************************************************
 */


class Pair {//not thread safe

    private int x,y;

    public Pair(int x, int y) {
        this.x = x;
        this.y = y;
    }
    public Pair(){
        this(0,0);
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    public void incrementX(){
        x++;
    }
    public void incrementY(){
        y++;
    }

    public String toString(){
        return "x: "+x+",y: "+y ;
    }
    public class PairValuesNotEqualException extends RuntimeException{
        /**
         * Constructs a new runtime exception with {@code null} as its
         * detail message.  The cause is not initialized, and may subsequently be
         * initialized by a call to {@link #initCause}.
         */
        public PairValuesNotEqualException() {
            super("Pair values not equal:"+Pair.this);
        }

    }

    public void checkState(){
        if(x !=y){
            throw new PairValuesNotEqualException();
        }
    }

}


//Protect a Pair inside a thread-safe class

abstract class PairManager {
    AtomicInteger checkCounter = new AtomicInteger(0);
    protected Pair p = new Pair();

    private List<Pair> storage = Collections.synchronizedList(new ArrayList<Pair>());

    public synchronized Pair getPair(){
        //Make a copy to keep the original safe :
        return  new Pair(p.getX(),p.getY());
    }

    //Assume this is a time consuming operation
    protected void store(Pair p){
        storage.add(p);
        try {
            TimeUnit.MILLISECONDS.sleep(50);
        }catch (InterruptedException e) {

        }
    }

    public abstract void increment();


}

//Synchronize the entire method
class PairManager1 extends  PairManager{

    @Override
    public synchronized void increment() {
        p.incrementX();
        p.incrementY();
        store(getPair());
    }
}

// user a critical section  -- 临界区

class PairManager2 extends  PairManager{

    @Override
    public void increment() {
       Pair temp;
        synchronized (this){
            p.incrementX();
            p.incrementY();
            temp = getPair();
        }
        store(temp);
    }
}

class  PairManipulator implements Runnable{

     private PairManager pm ;

    public PairManipulator(PairManager pm) {
        this.pm = pm;
    }

    @Override
    public void run() {
        while (true){
            pm.increment();
        }
    }

    public String toString(){
        return "Pair: " + pm.getPair() + " checkCount = " + pm.checkCounter.get();
    }
}

class PairChecker implements  Runnable {

    private PairManager pm ;

    public PairChecker(PairManager pm) {
        this.pm = pm;
    }

    @Override
    public void run() {
        while (true){
            pm.checkCounter.incrementAndGet();
            pm.getPair().checkState();
        }

    }
}



public class CriticalSection {
    // Test the two different approaches -- 方法
    static void testApproaches(PairManager pman1,PairManager pman2){
        ExecutorService exec = Executors.newCachedThreadPool();

        //Manipulator 机械手
        PairManipulator
                pm1 = new PairManipulator(pman1),
                pm2 = new PairManipulator(pman2);

        PairChecker
                pcheck1 = new PairChecker(pman1),
                pcheck2 = new PairChecker(pman2);

        exec.execute(pm1);
        exec.execute(pm2);
        exec.execute(pcheck1);
        exec.execute(pcheck2);
        try {
            TimeUnit.MILLISECONDS.sleep(500);
        } catch (InterruptedException e) {
            System.out.println("Sleep interrupted");
        }
        System.out.println("pm1:"+pm1+"\n pm2:"+pm2);
        System.exit(0);

    }

    public static void main(String[] args) {
        PairManager
                pman1 = new PairManager1(),
                pman2 = new PairManager2();

        testApproaches(pman1,pman2);

    }

}
